'Rogue' star slowly heading our way

A nearby star will very likely make a close encounter with our solar system in more than a million years' time, according to a new study.

Gliese 710 could disrupt the orbits of the outer planets, according to new calculations. ((ESO/ABC) )

The star, known as Gliese 710, could disrupt planetary orbits and send a shower of comets and asteroids toward the inner planets when it passes in 1.5 million years time.

Vadim Bobylev of the Pulkovo Astronomical Observatory in St. Petersburg is the author of the study, which appears on the prepress website arXiv and has been submitted to the journal Astronomy Letters.

He estimates that the likelihood of an impact between Gliese 710 and the outer edge of our solar system to be as high as 86 per cent.

"That's about as close to certainty as this kind of data can get," said Bobylev.

Bobylev bases his calculations on data collected by the European Space Agency's Hipparcos spacecraft.

Measurements made by the spacecraft were used to create the Hipparcos catalogue, which contains detailed position and velocity measurements of 100,000 stars in our neighbourhood.

According to the catalogue, there are 156 stars that either have or will make a close approach, which appear to occur once every two million years.

In 2007, the Hipparcos data was revised and combined with new measurements of star velocities.

Bobylev combined this data with several new databases, finding an additional nine stars that either have had, or will have, a close encounter with the sun.

'Likely to have serious consequences'

When he took a closer look at Gliese 710, he was shocked.

"There is an 86 per cent chance that [Gliese 710] will plough through the Oort Cloud of frozen comets that surrounds the solar system," he wrote.

"Being half a parsec [about 1.6 light years] away makes it sound like little more than a graze, but it's likely to have serious consequences. Such an approach is likely to send an almighty shower of comets into the solar system which will force us to keep our heads down for a while."

Paul Dobbie of the Anglo Australian Observatory, said our solar system has had a number of close encounters.

"It's not the only stellar visitor to come to the 'hood," he said. "About half a million years ago Gliese 208 passed within about four light years of the sun."

While that was closer than our Sun's closest neighbours Alpha and Proxima Centauri, it was far enough away to leave our solar system untouched.

But Dobbie says the predicted path of Gliese 710 will make this a certain close encounter.

"There are a few more objects that will pass within a few light years of our sun, but none this close," he said.